Activity concentrations of222Rn,220Rn, and their decay products in german dwellings, dose calculations and estimate of risk

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Abstract
Measurements of the concentrations of222Rn, its short-lived decay products and of212Pb -212Bi were performed in 150 dwellings and in the open air in the Federal Republic of Germany. The concentration of222Rn was measured by electrostatic deposition of218Po. The concentrations of the short-lived decay products were measured by air sampling and alpha-spectroscopy. It was found that inside dwellings the average potential alpha-energy concentration of the short-lived daughters is about three times higher than in the open air. The total potential alpha-energy concentration indoors amounts to 2.6 · 10−3 Working Level (W. L.). Direct measurements of the equilibrium factor inside dwellings gave a mean value of 0.3. A strong dependence of the potential alpha energy concentration on the ventilation rate in dwellings has been observed. These ventilation effects exceed the effects caused by differences in the activity concentrations due to different building materials. The dose calculation results in an average dose to the whole lung due to the inhalation of short-lived radon daughters of about 0.05−0.2 mGy/a. An estimate of risk - based on the risk factors for uranium miners - shows an average lifetime risk of about 6 · 10−4 for the incidence of lung cancer caused by inhalation of radon and thoron daughters in dwellings in the Federal Republic of Germany.